1. Technical Field
The present invention relates to a successive comparison type analog-to-digital converting apparatus for converting an analog signal into a digital signal.
2. Description of the Related Art
Cross references related to the successive comparison type analog-to-digital converting apparatus are as follows:
(a) Japanese Unexamined Patent Publication (Kokai) No. 63-248221 published on Oct. 14, 1988, disclosing a conventional successive type analog-to-digital converter having means for correcting an output digital code;
(b) Japanese Unexamined Patent Publication (Kokai) No. 62-133819 published on June 17, 1987, disclosing an analog-to-digital converter which can attain a high accuracy by the use of an A/D converter with a small bit number;
(c) Japanese Unexamined Patent Publication (Kokai) No. 61-284117 published on Dec. 15, 1988, disclosing a conventional successive comparison type analog-to-digital converter in which, to attain a high speed operation, a simplified circuit construction and ability to operate with a single clock signal, latching means are appropriately provided;
(d) Japanese Unexamined Patent Publication (Kokai) No. 60-170329 published on Sept. 3, 1985, disclosing a conventional successive comparison type analog-to-digital converter in which, to attain a decreased number of circuit elements and cost, and to realize an efficient use of space and high accuracy, successive comparisons are effected by the use of several reference voltages;
(e) Japanese Unexamined Patent Publication (Kokai) No. 60-66524 published on Apr. 16, 1985, disclosing a conventional successive comparison type analog-to-digital converter in which, to attain a high speed operation and high accuracy, D/A converters with small bit numbers are employed;
(f) Japanese Unexamined Patent Publication (Kokai) No. 53-109463 published on Sept. 25, 1978, disclosing a conventional successive comparison type analog-to-digital converter in which, to attain a high speed operation and a simplified circuit, a divisional circuit and an analog subtractor are employed instead of a D/A converter; and
(g) Japanese Unexamined Patent Publication (Kokai) No. 52-119161 published on Oct. 6, 1977, disclosing a conventional analog-to-digital converter by which the dynamic range is expanded without deteriorating the accuracy.
In a conventional successive comparison type analog-to-digital converting apparatus, when an n-bit analog-to-digital converting apparatus is to be formed, an n-bit digital-analog converter is necessary. The digital-analog converter, however, has a problem in that the size and cost rapidly increase depending on the number of bits.
Also, to decrease the cost of the analog-to-digital converting apparatus, if the number of bits of the digital-analog converter is decreased, there is a problem in that the accuracy of the converted digital value is reduced as later described in more detail with reference to the drawings.